1. Field of the Invention
The present invention relates to a semiconductor device utilizing a copper wiring and a method of manufacturing the semiconductor device.
2. Description of the Background Art
In a system LSI in the 0.13 xcexcm gate generation and subsequent thereto, it is important that a signal delay of a device should be reduced to implement an increase in the speed of the device. The signal delay of the device is represented by the sum of a signal delay of a transistor and a wiring delay. As a wiring pitch is reduced rapidly, the influence of the wiring delay becomes greater than that of the signal delay of the transistor.
Since the wiring delay is proportional to a product of RC (a resistance by an interlayer electrostatic capacity), it is necessary to reduce a wiring resistance or to decrease a capacity of an interlayer insulating film in order to relieve the wiring delay. In order to solve the problem, accordingly, there has been vigorously studied a buried wiring structure employing a combination of a low permittivity interlayer insulating film and a copper wiring having a low resistance.
FIG. 19 is a view showing a semiconductor device having a general buried copper wiring structure according to a conventional example. In the semiconductor device, a copper wiring having two layers is formed.
More specifically, a lower insulating layer 112 including an element (not shown) such as a transistor is formed on a substrate 111 such as a silicon substrate. A first etching stop film 113, a first low permittivity interlayer insulating film 114 and a first hard mask film 115 are formed on the lower insulating layer 112.
The first etching stop film 113 serves to stop etching when forming a wiring trench in the first low permittivity interlayer insulating film 114. Moreover, the first hard mask film 115 is used as a hard mask (a mask formed of a stronger material than a photoresist) for forming the wiring trench in the first low permittivity interlayer insulating film 114.
A wiring trench is formed in the first low permittivity interlayer insulating film 114 and the first hard mask film 115, in which a first barrier metal 116 and a first copper wiring 117 are formed.
In the structure, furthermore, a first copper diffusion preventive film 118, a second low permittivity interlayer insulating film 119, a second etching stop film 120, a third low permittivity interlayer insulating film 121, and a second hard mask film 122 are formed.
The first copper diffusion preventive film 118 is provided for preventing the diffusion of copper. The copper is diffused into an insulating film more easily than a material such as aluminum, titanium or tantalum. When a large amount of copper is diffused into the interlayer insulating film, the interlayer insulating film causes a dielectric breakdown. Therefore, it is necessary to prevent the diffusion of the copper.
A silicon nitride film (a relative permittivity of 6.5 to 8.0) having a copper diffusion preventing capability, a silicon carbide film (a relative permittivity of 4.5 to 5.0) or the like is employed for the first copper diffusion preventive film 118. It is preferable to employ a silicon carbide film having a great effect of decreasing the capacity of the interlayer insulating film (that is, a low relative permittivity).
The second etching stop film 120 serves to stop etching when forming a wiring trench in a third low permittivity interlayer insulating film 121.
Moreover, a second hard mask film 122 is used as a hard mask for forming a wiring trench in the third low permittivity interlayer insulating film 121.
A wiring trench is formed in the third low permittivity interlayer insulating film 121 and the second hard mask film 122, and furthermore, a connecting hole is formed in a part of the second etching stop film 120 exposed to a wiring trench 124 and the third low permittivity interlayer insulating film 119. A second barrier metal 125 and a second copper wiring 126 are formed in the wiring trench and the connecting hole.
Furthermore, a second copper diffusion preventive film 127 is formed in the structure. Examples of an applicable material to this film include a silicon nitride film, a silicon carbide film and the like. It is preferable to apply the silicon carbide film having a great effect of decreasing a capacity of an interlayer insulating film in the same manner as the first copper diffusion preventive film 118.
In a semiconductor device employing the copper wiring, it is preferable that the silicon carbide film should be applied as the copper diffusion preventive film as described above. As compared with a silicon nitride film to be another candidate material, the silicon carbide film has a lower relative permittivity and produces the greater effect of decreasing the capacity of the interlayer insulating film.
However, the silicon carbide film cannot completely prevent copper from being diffused. For example, a copper diffusion preventing function becomes insufficient due to the presence of an impurity in the silicon carbide film and the copper diffusion preventing function is deteriorated by a secular change.
In order to enhance the reliability of the semiconductor device, therefore, it is always required that the copper diffusion preventing capability of the silicon carbide film should be enhanced and the insulating film should have a long lifetime maintained until a dielectric breakdown is caused by the diffusion of the copper.
It is an object of the present invention to provide a semiconductor device having a copper wiring structure in which a copper diffusion preventing capability of a silicon carbide film can be improved and a lifetime maintained until a dielectric breakdown is caused by copper diffusion can be increased, and furthermore, a method of manufacturing the semiconductor device.
An aspect of the present invention is directed to a semiconductor device including an interlayer insulating film, an electric conductor containing copper as a main component, and a silicon carbide film. The silicon carbide film is provided between the electric conductor and the interlayer insulating film, and the silicon carbide film contains oxygen atoms in 30 atomic % or more.
According to the present invention, the silicon carbide film contains oxygen atoms in 30 atomic % or more. Consequently, it is possible to improve the function of the silicon carbide film for preventing copper employed for the electric conductor from being diffused into the interlayer insulating film. Thus, it is possible to obtain a semiconductor device which maintains a long lifetime until a dielectric breakdown is caused by the diffusion of the copper.
Preferably, in the semiconductor device according to the present invention, the silicon carbide film also contains nitrogen atoms, and the silicon carbide film contains oxygen atoms and nitrogen atoms in 30 atomic % or more.
According to the present invention, the silicon carbide film also contains nitrogen atoms. The silicon carbide film contains oxygen atoms and nitrogen atoms in 30 atomic % or more. Also in this case, the same effects as those in the above-mentioned aspect of the present invention can be obtained.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.